Hi David
Are you working for a distillery or are you trying to get work there?
As mentioned BS7671/ATEX. Compex certification for electricians working in zones. The process team or chemical engineer should be able to help define/identify zones on your site. The generic model of zones covered in compex is a good start.

Start with that and drill down from there - the hazardous area classification is not yours to determine - the client should do that for you - as the designer/installer, you need to respond to that zoning arrangement by design and material/equipment selection/installation.